Method for making readily filterable viscose



Patented July 28, 1953 METHOD FOR MAKING READILY FILTERABLE VISCOSEErich 'Iorke,. Hamburg, and Werner Matthaes,v Krefeld (Rhine), Germany;assignors to Phrix- Werke, A. G., Hamburg, Germany, a corpora tion ofGermany No Drawing. Application December 2, 1950-, Serial No. 198,906.In Germany May 7, 1949 8 Claims. It;

This invention relates to method for making readily filterable viscose.

It more particularly relates to the manufacture of. readily filterableviscoses, which can be spun into threads and films.

In the methods generally used for this purpose in the industry,cellulose or linters are impregnated with about 10 times by weight of a1:6 26-% sodium hydroxide solution, squeezed 01f to approximately 3vtimes the weight of the pulp used, and the fibers. disassociated. Thealkali cellulose are then air-aged and placed in rotary drums orkneadingdevices for sulfiding. Sulfidin (xanthating) is carried out forabout 90 minutes at 1'6-28 C., whereupon solvent lye or solvent water isadded in portions during 3 hours in order to avoid the formation oflumps.

The drum method, as heretofore carried. out, has the disadvantage that:the dissolving of the xanthogenate must be eifected in a separateapparatus. This disadvantage can, be avoided by sulfi'din in the churn,but considerable power must be used for the churning of the mass whichis initially crumbly and becomes rubberlike in the last stage of thesulfi'ding.

The disadvantages of the two methods are avoided by the method:described in the following. In the method according to the invention,there is added to the alkali cellulose prior to or during thesulr'iding, at least to and preferably or more of the solvent lye andthe solvent water, i. e., of the total diluent liquid. The alkalicellulose may be obtained in known manner by impregnating the pulp orlin-ters with 16-26% sodium hydroxide solution. The formation ofrubberlike tough masses during the sulfiding is avoided in this way andat the same time the Xanthogenate obtained is entirely or partiallydissolved in the course of the sulfiding reaction. In this connection,it is essential that the sulliding temperature beabove 20 C. However, itmust also not be too high and should not be more than 40 C. As a rule,the sulfiding is carried out at 26-30 C. For example, the sulfiding iscommenced at 20-23 C. and. the temperature at the end of the reaction ispermitted to rise to 26-29 C. However, it is also advantageous,particularly in order to obtain the shortest possible sulfiding anddissolving times, to carry out an isothermal sulfiding in thetemperature range between 20-40 C. and preferably between 26-30 C.

Methods have already been describedv in connection with which a pastyalkali cellulose, is sulfided but in this case. the sulfiding, iseffected at 5-12" 0., In this way viscoses having the customarycellulose and alkali concentration were not obtained. Furthermore,mercerizing lyes of low alkali concentration were used, which rendersthe production of a readily sulfided alkali cellulose dii-ficult.

In the method according to the present invention, the alkali cellulosecan be diluted prior to the commencing of the sulfiding by the additionof the corresponding quantity of solvent lye and solvent Water. Theshortest manufacturing times are however had if the solvent lye andsol-vent water are continuously added at the very' start of thesulfiding. However, it is also possible to first sulfide the alkalicellulose in dry conditionv for ashort period of time, for instance,5-15- minutes, and, then effect the dilution.

In the method according to the invention, the alkalizing can also beeffectedin such manner that only enough 16-26% mercerizing lye, iscaused to act on the cellulose as to render a squeezing off of excesslye unnecessary. In order to obtain good alkalizing and rapid sulfiding,it may be advisablein. this connection to add to the alkalizing lye awetting agent, as for instance, sulfonated castor oil, or else to add anorganic liquid which is soluble in the lye and in carbon disulfide, suchas, for example, methanol, glycol, orglycerine, in small quantities, forexample, 1-10 cc. per kg. cellulose. The addition of the wetting agentand of the organic liquid can also be made to the carbon disulfideduring the sulfiding.

These wetting agents, and in particular abietic acid, also act toimprove the degree of disassociation of the fibers. They can thereforealso be added: during the disassociation process. A good disassociationof the alkali cellulose fibers is essential for the wet sulfidingmethod,particularly if the alkalizing is effected without excess lye. Whenusing low polymer pulp having a polymerization degree of about 250-400,and alkalizingwithout excess lye, there can be directly obtained bydilution, without ageing,v a spinnable viscose of ordinaryconcentration. If pulps of higher degrees of polymerization are used,for example 600-1000, the alkali cellulose must be subjected to anageing, which is preferably carried out at elevated temperatures, forexample 35-80" C. In order to shorten the ageing, it is advantageous tocause suitable oxidizing or reducing agents to act on the alkalicellulose at elevated temperatures, for example, 3050 C., in.

which connection the oxidizing or reducing agents can be added to thealkalizing caustic or be permitted to trickle down in aqueous solutiononto the alkali cellulose. Suitable oxidizing agents are persulfate,percarbonate and hydrogen peroxide. Examples of suitable reducing agentsin accodance with the invention are sodium sulfide, sodium sulfite,sodium nitrite, hydroquinone or phenylhydrazine.

The method can be carried out suitably in a conventional churn, or insimple agitator provided with a temperature jacket, although atemperature jacket is not necessary in all cases. The method can also becarried out in a rotating drum. A horizontal agitator is found tofunction particularly advantageously. The introduction of the pulpsheets, if the alkalizing is efiected without lye excess, can take placetherein directly or after they have been subjected to a lye-tricklingtreatment. The lye-trickling treatment in this connection suitably takesplace on a chute provided on the agitator, through which chute the pulpsheets are fed to the receptacle. However, the pulp can also beintroduced dry and the agitator be filled with the lye. Thedisassociation of the fibers of the cellulose is effected by theagitator blades or the agitator arms which pass close to the wall of thevessel. An oxidizing or reducing ageing can be simultaneously connectedwith the alkalizing, the oxidizing or reducing agents being added to thetrickling lye or the prior lye, or being permitted to trickle in aqueoussolution down onto the alkali cellulose.

An exact maintaining of the sulfiding temperature is necessary inconnection with wet sulfiding. At temperatures below 28 C., the carbondisulfide is emulsified in the pasty alkali cellulose. If thetemperature increases substantially above 28, the vapor pressure of thecarbon disulfide, which has a boiling point of 46 C., increases toorapidly and the carbon disulfide passes to a considerable extent out ofthe emulsion. At a lower sulfiding temperature of less than thesulfiding velocity of the alkali cellulose is too low and the carbondisulfide passes mainly into the side reactions. However, with the highreaction velocity of the pasty alkali cellulose, the sulfidingtemperature can be increased to 3540 C. without the carbon disulfideconcentration in the alkali cellulose paste becoming too low to effectthe uniform impregnation and emulsifying of the carbon disulfide. Thecarbon disulfide may be added to the alkali cellulose when the cellulosetemperature is 16 to 20 C. and the temperature may then be increased toabout 24 C. for the rapid initiation of the sulfiding reaction.

In the method according to the invention, the

sulfiding temperature can be controlled by suitably controlling thetemperature of the solvent lye and solvent water added, as is also trueof the temperature of the alkali cellulose subjected to the sulfiding.The shortest sulfiding and dissolving times are obtained if thesulfiding temperature does not drop below 26 C. during the course of thesulfiding. Preferably, the temperature of the alkali cellulose, thespeed of addition and temperatures of the solvent water and solvent lyeare so regulated that the sulfiding reaction takes place at atemperature between 26 and 30 C. With this manner of operation,sulfiding and dissolving times of 20 to minutes can be obtained.

The addition of the solvent lye water may take place during the first 20to 60 minutes after the commencement of the sulfiding. As alreadymentioned, the addition of the solvent lye water may also be commencedbefore the beginning of iii the sulfiding. The alkali cellulose usedaccording to the invention may be obtained in the customary manner byalkalizing with excess lye and squeezing off the excess lye, alkalicellulose so obtained must of course be subjected to an air ageing. Ifthe ageing of the alkali cellulose takes place in an accelerated processat elevated temperatures, as for example, at 30 to 45 C., the sulfidingcan be commenced directly after the degradation has taken place withoutcooling the alkali cellulose, the temperature of the solvent lye and ofthe solvent water being chosen accordingly. With an alkali cellulosetemperature of 35 C., the temperature of the solvent lye is, forinstance, adjusted to 35 C., as is the temperature of the solvent water.Inasmuch as it is necessary to cool the cellulose after the sulfiding iscompleted in order to avoid a strong ripening of the viscose, it is alsopossible to add cold solvent lye toward the middle or end of thesulfiding, in order to reduce the final temperature of the viscoseobtained. In the carrying out of the sulfiding, the heat capacity of thesulfiding vessel and the quantities of heat generated by the churning oragitating mechanism must be taken into consideration in connection withthe adjustment with the desired sulfiding temperature. This quantity ofheat is naturally considerably less in connection with the pasty massthan in connection with the previous methods of dry sulfiding.

The method of the invention is further explained by the followingexamples:

Example 1 4000 grams of an alkali cellulose which were obtained from aspruce sulfite pulp by alkalizing with 18% NaOH in excess with a liquorratio of 1/ 10, the excess lye being pressed off, are sulfided in anagitating vessel after 17 hours ageing at 34 C. The alkali cellulose hasan alpha content of 25.1% and 17.2% NaOH. Prior to the sulfiding, thealkali cellulose is diluted by the addition of 2260 cc. water and 1950cc. solvent lye grams NaOI-I per liter) to 10.5% NaOH, and sulfidedafter prior cooling to minus 3 C. for 50 minutes at 20 to 28 C. By theaddition of 3500 cc. water during the course of 180 minutes, there isobtained at 10 to 15 C. a viscose containing 8.4% cellulose in additionto 7.2% NaOI-I and 33.5% CS2. The viscose has a viscosity of 39 secondsand a filtration constant of 174. The filtration capacity is 460 litersper minute. The viscose is spun at an ammonium chloride number of 11 andgives a fiber having a breaking load of grams per denier and 23%elongation. The degree of polymerization of the fiber is 280.

Example 2 75 kilos of a rayon-sulfite-spruce-pulp (alpha content 88.5%,polymerization degree 800) are churned at 20 C. with 260 liters of asodium hydroxide solution to which 400 cc. of Monopol Brillant Oil(sulfonated castor oil or some other suitable wetting agent in therequired amount) have been added and which contains 240 grams per literNaOH, for two hours and then aged for 1'7 hours at 34 C. mixed in achurn or agitating vessel with 248 liters of water with the simultaneousaddition of 16 liters CS2 and thereupon sulfided for 70 minutes at 20 to28 C'. By the addition of 113 liters of water, there is then obtained aviscose having a viscosity of 36 seconds and a cellulose content of 8.3%in addition to 6.8% NaOH. The viscose is easily filtered (filtrationconstant in accordance with the Convention Method of 89) and givesthreads of normal strength when spun in a Muller bath.

Example 3 700 grams of a synthetic fiber-spruce-sulfitepulp of apolymerization degree of 750 are coarsely comminuted in a xanthogenatechurn. Over this there is poured a mixture of 2300 cc. lye (240 r msNaOH per liter) and 2000 cc. water, heated to 80 C. in which 5 cc. ofthe wetting agent known under the trade name of Monopol Brillant Oil orsome other wetting agent has been poured, and churning is efiected forone hour. After cooling to C. sulfiding is effected for 90 minutes with260 grams of carbon disulfide. Thereupon a further 3000 cc. of water areadded in the course of 3 hours and a viscose is obtained containing 8%cellulose, 7% NaOH and carbon disulfide (referred to alpha cellulose).The viscose does not have any swollen fibers. The viscosity is 89seconds, the filtration constant 127 (KW) and the filter capacity 260liters per minute.

Example 4 The manner of operation is the same as the one indicated inExample 3, with the only difference that 75 grams NazS (referred toanhydrous sodium sulfide) are added to the 80 lye. In this way, a strongdecrease in the viscosity is obtained. The viscosity of of the viscoseobtained is 39 seconds with a cellulose content of 8% in addition to 7%NaOH; KW 198, filtration capacity 304 liters per minute. The viscose isspun in the customary manner in a Muller bath and gives a fiber of a drystrength of 160 grams per denier and 20% dry elongation. Thepolymerization degree of the fiber is 350. The alkali solubilitycorresponds to that of a viscose synthetic fiber spun in accordance withconvention method.

Ewamnle 5 1000 grams of a spruce-sulfite-pulp (alpha content 886%,degree of polymerization 600) are alkalized with 3.5 liters NaOI-I (240grams NaOH per liter) containing 2 cc. Monopol Brillant Oil per liter,at 20 C. for 2 hours in an agitating vessel and thereupon diluted to aNaOI-I content of about 11% by the addition of 3 liters of water.Thereupon sulfiding is effected for 70 minutes at 20 to 28 C". with 350cc. of CS2 and by the addition of the corresponding quantity of solventwater, there is obtained a viscose containing 7.5% alpha and 7.5%NaOI-I. The viscosity of the viscose is 940 seconds (measured at 18according to the convention method with a steel ball of 3 mm. diameterand a distance of fall of 20 cm). The viscose is ripened to a salt pointof 0.1% and after setting aside for three days at 20 C'., is spun undera pressure of 8.5 atmospheres guage according to the funnel spinningprocess through nozzles of a width of 0.8 mm., into water of atemperature of 20 C. The drawing-01f velocity is 80 meters. Afterleaving the precipitating funnel, the thread which passes over a guidebar, passes through a setting bath containing 3% H2804 and 5% N azSOe.During the spinning process, the viscose feed is adjusted in such amanner that a fiber thickness of 3.6 denier is obtained. The strength ofthe spun fiber is 1.6 to 2 grams per denier and the elongation isbetween 12 and 18%.

Eazample 6 kilos of alkali cellulose of an alpha cellulose content 01 25to 29%, for example 25.6%,. and a caustic soda content of 16.5 to 17.5for example 17.1%, produced from a rayonspruce-sulfitepulp of apolymerization degree of 750 (alpha cellulose content 88.5%) by steepingin a sodium hydroxide solution containing 240 grams caustic soda perliter in a liquor ratio of 1 to 10- with the squeezing 01f of the excesslye are introduced after 17 hours ageing at 34 C. into an xanthatechurn. To the alkali cellulose cooled to 28, there are added 4.5 literscarbon disulfide. With the churning and agitating mechanism operating,29 liters of solvent lye (9% caustic soda) of 29 C., are permitted toflow in over a period of 10 minutes and thereupon 75 liters of water of29 C. are introduced over a period of 20 minutes. After the addition ofall the solvent lye and all the solvent water, the dissolving iscontinued for a further 5 minutes, During the entire sulfiding anddissolving, the temperature of the reaction mixture stays at 29 C. Theviscose obtained has a filtration value of 63, and after a further 25minute of dissolving, it has a filtration value of 47. The viscose doesnot contain any swollen fiber, has a cellulose content of 8.3%, acaustic soda content of 6.4% and a viscosity of 20. The polymerizationdegree of the film precipitated from the viscose is 299. The totalsulphur in the viscose corresponds to 32% carbon disulfide referred toalpha cellulose.

Example 7 40 kilos of alkali cellulose of 29 C. produced in the samemanner as indicated in Example 6, are mixed in the churn with 25 liters9% solvent lye and 5 liters water, both of 29 0., and thereupon 3.5liters of carbon disulfide are added. Sulfiding is effected for 20minutes, the temperature rising to 31 C. Thereupon, the remaining50liters of 15 C. solvent water are added over the course of 12 minutes,due to which any decrease in the temperature of the viscose obtained isobtained simultaneously with the dissolving. Dissolving is continued for20 minutes after the addition of the rest of the solvent water. Theviscose obtained has the same composition as the one according toExample 6 and has a filtration value KW of 83.

Example 8 50 kilos of cellulose (alpha cellulose content 88.5%.polymerization degree 750) are brought by a chute into an agitatingvessel in which there are contained liters of 19.5% sodium hydroxidesolution in which 1.5 kilos of sodium sulfide (anhydrous NazS) aredissolved. The pulp sheets fill up with lye and are converted into afiber paste by the passing of the agitator blades close by the vesselwall. Alkalizing is efiected for one hour at 40 C. Thereupon, 15 litersof carbon disulfide are added andat the same time or immediately afterthe. addition of. 270 liters of water of 20 C. are permitted to run intothe sulfiding vessel over the course of 20 minutes, the rate ofadmission being so. regulated that the temperature of the reactionmixture is maintained at. 27 C. There is obtained a viscose of aviscosity of i5 seconds and an alpha cellulose. con.- tent of 8.5%caustic soda. Thev viscose can readily be filtered and has a filtrationvalue of 90.

tent of 25 to 29%. for example, 25.5%, and an NaQI-E content of 16.5 to17.5%, for example,

17.1%, made from a rayon-spruce-sulfite-pulp of a polymerization degreeof 750 (alpha content 88.5%) by steeping in a sodium hydroxide solutioncontaining 240 grams NaOH per liter in a liquor ratio of 1 to 10 withthe squeezing off of the excess lye, are diluted after 17 hours ageingat 34 C. in a xanthate churn by the addition of 4550 cc. of water to 8%NaOI-I. The alkali cellulose paste of a temperature of 23 to 24 C. issulfided for 50 minutes with 360 grams carbon disulfide, the temperaturerising to 28 C. By the addition of 2200 cc. solvent lye (100 gramsNaOI-I per liter) and 1550 cc, Water during the course of 90 minutes,there is obtained a viscose containing 6.6% NaOH and 8% cellulose. Theviscose has a viscosity measured according to the convention method of22 seconds, a filtration constant of 40, and a filtration capacity of908 liters.

The viscose can be readily filtered and spun and gives a thread of a drystrength of 145 grams per denier and elongation.

Example 10 An alkali cellulose produced and aged as indicated in Example9 is diluted in a quantity of similarly 4000 grams by the addition of2260 cc. Water and 1950 cc. solvent lye (100 grams NaOl-I per liter) to10.5% NaOI-I and sulfided in an agitating vessel for 30 minutes at 20 to28 C. By the addition of 3500 cc. water, there is obtained a viscosecontaining 8.4% cellulose in addition to 7.2% NaOH and 33.5% CS2, Theaddition of the water is effected within 5 minutes. After 30 minutespumping in order to obtain more rapid dissolving and homogenizing, thereis obtained a viscose having a viscosity of 30 seconds and a filtrationconstant measured by the convention method of 90. The polymerizationdegree 01 the fiber obtained from a viscose by spinning in aconventional Muller bath is 280.

Example 11 17, kilos of alkali cellulose prepared and aged in the mannerindicated in Example 9, are

churned in an agitator vessel provided with a pumping line for a fewminutes with 6 liters of viscose is easily filterable and has afiltration value of 50.

Example 12 kilos of alkali cellulose prepared in the manner indicated inExample '7 are introduced into a rotating drum (alpha content of thealkali cellulose 24.8%, NaOH content 17.1%, temperature 27). After theclosing and evacuation of the drum, 31.5 liters CS2 are permitted tofiow in during rotation and thereupon 200 liters of solvent lyecontaining 100 grams NaOH per liter and 100 liters of water, both of 30C., are added over the course of 10 minutes. sulfiding is continued foran additional 30 minutes without any addition, and thereupon a furtheramount of 250 liters of water are added over the course of 20 minutes.By the addition of a further 250 liters of water of 30 0., there isobtained within 10 minutes, a viscose containing 8% cellulose and 7%NaOH and having a viscosity of 30 seconds. If necessary, the viscose canbe further dissolved for a After the addition of 23.1 liters shortperiod of time, for instance, one hour in a dissolver or high speedmixer, or can be worked on by a crushing pump for further homogenizing.The viscose is easily filterable and has a KW value of 115. It isadvantageous to subject the alkali cellulose to a good shredding priorto the sulfiding.

The above examples are given by way of illustration only, the inventionbeing limited by the claims.

For the purpose of the above description, the viscosity of a spinningsolution is defined in Goetze Kunstseide und Zellwolle, pages 262-263.The viscosity is equal to the time needed by a ball to fall through thespinning solution. For example a viscosity of 30 means that the timewhich the ball needs to fall through the solution is 30 seconds. Aspecial ball of a diameter of 3.160 millimeters and a weight of 129-131milligrams is used for this purpose. The ball has to fall through aheight of 200 millimeters of solution at a temperature of 20 C.

Liquor ratio means the quantity of liquid in liters which is used forsolving one kilogram of solid matter. For example a liquor ratio of 3means that one kilogram of cellulose pulp is alkalized with 3 liters ofcaustic soda solution.

The polymerization degree is defined in Goetze (see above) pages 31-36.The polymerization degree is measured by means of a diluted ammoniasolution of copper hydroxide. The polymerization degree will be arrivedat by dividing the time which such a solution containing cellulose needsto pass a viscosity meter by the respective time needed by the purecopper hydroxide ammonia solution.

The filter capacity KW is defined in the publication of Hermans and H.L. Bredes Rec. Trav. chim. 547-548, 680, 1935. The KW value is equal tothe number of cubic centimeters of a spinning solution passing astandard filter in a fixed time.

The salt point is a measure for the degree of ripeness of a spinningsolution. It is defined in Goetze (see above) page 289. The method isbased on the fact that the coagulation speed of a viscose increases withthe degree of ripeness. To determine the salt point it is necessary todrop a solution of sodium chloride of decreasing concentrations into thespinning solution. The salt point is reached at that concentration ofthe sodium chloride solution at which the viscose no longer coagulates.

We claim:

1. In the method for making readily filterable viscose by the sulfidingat a temperature of 20 to 40 C. with carbon disulfide of an alkalicellulose produced by the impregnation of cellulose with a 16-26%caustic solution, and having a degree of polymerization corresponding toan alkali cellulose produced from cellulose with a polymerization degreeof about 250 to 400, and the addition of a solvent selected from thegroup consisting of lye and Water to the resulting xanthagenate for theformation of viscose, the improvement which comprises adding at leastone fifth of said solvent after the completion of the carbon disulfideaddition for said sulfiding and efiecting said sulfiding in the presenceof said solvent.

2. Improvement according to claim 1 in which at least one fifth of saidsolvent is added immediately after the completion of the addition ofcarbon disulfide for said sulfiding.

3. Improvement according to claim 1 in which at least one fifth of saidsolvent is added about 5 9 to 15 minutes after the beginning of saidsulfiding.

4. Improvement according to claim 1 in which at least one fifth of saidsolvent is added continuously over a period of about 10 to 30 minutes.

5. Improvement according to claim 1 in which said sulfiding is effectedin the presence of a wetting agent at a temperature of about 26 to 30 C.

6. Improvement according to claim 5 in which said alkali cellulose is apre-ripened alkali cellulose of a degree of polymerization correspondingto the degree of polymerization of an alkali cellulose prepared withoutpre-ripening from cellulose with a degree of polymerization of about 250to 400.

7. Improvement according to claim 1 in which at least one fifth of saidsolvent is added within 5 to minutes after the beginning of saidsulfiding and in which said sulfiding is effected at a temperature of 26t 30 C., the viscose formed by the addition of the remainder of saidsolvent after the xanthagenate formation having a cellulose contenthigher than its alkali content.

8. Improvement according to claim 1 in which said alkali cellulose is apre-ripened alkali cellulose having a polymerization degreecorresponding to the polymerization degree of an alkali celluloseproduced from a cellulose having a polymerization degree of about 250 to400 without pro-ripening.

ERICH 'I ORKE. WERNER MATTHAES.

References Cited in the file of this patent UNITED STATES PATENTS NumberRe. 22,459 1,279,329 1,435,650 1,857,948 1,862,592 10 1,955,2992,064,356 2,068,631 2,076,594 r 2,076,595 2,106,812 2,114,605 2,126,9762,139,302 2,222,050 2,513,652 2,542,285

Name Date Schlosser et a1. May 30,1944 Glover et a1 Sept. 17, 1918Mitscherling Nov. 14, 1922 Dosne May 10, 1932 Goth June 14, 1932 Kampfet al. Apr. 7, 1934 Picard et al. Dec. 15, 1936 Richter Jan. 19, 1937Richter Apr. 13, 1937 Ritcher Apr. 13, 1937 Richter et al Feb. 1, 1938Nicoll Apr. 19, 1938 Richter et a1 Aug. 16. 1938 Booys Dec. 6, 1938Stoeckly et a1 Nov. 19, 1940 Kline July 4, 1950 Mitchell Feb. 20, 1951OTHER REFERENCES Heuser, Cellulose Chemistry, 1944, pages 319, 320, 325to 327.

1. IN THE METHOD FOR MAKING READILY FILTERABLE VISCOSE BY THE SULFIDINGAT A TEMPERATURE OF 20* TO 40* C. WITH CARBON DISULFIDE OF AN ALKALICELLULOSE PRODUCED BY THE IMPREGNATION OF CELLULOSE WITH A 16-26%CAUSTIC SOLUTION, AND HAVING A DEGREE OF POLYMERIZATION CORRESPONDING TOAN ALKALI CELLULOSE PRODUCED FROM CELLULOSE WITH A POLYMERIZATION DEGREEOF ABOUT 250 TO J00, AND THE ADDITION OF A SOLVENT SELECTED FROM THEGROUP CONSISTING OF LYE AND WATER TO THE RESULTING XANTHAGENATE FOR THEFORMATION OF VISCOSE, THE IMPROVEMENT WHICH COMPRISES ADDING AT LEASTONE FIFTH OF SAID SOLVENT AFTER THE COMPLETION OF THE CARBON DISULFIDEADDITION FOR SAID SULFIDING AND EFFECTING SAID SULFIDING IN THE PRESENCEOF SAID SOLVENT.